Temperature indicator



Jan. 3, 1939. W W, PARKER 2,142,677

TEMPERATURE INDICATOR Filed Oct. 3Q. 1935 valain im.. 3, 1939 2,142,677

UNlTED STATES PATENT o l-Flcs TEIWPERATURE INDICATOR Washington W. Parker, Chicago, Ill., assignor to t Schweitzer & Conrad, Inc., Chicago, Ill., a corporation of Delaware Application October 30, 1935, Serial No. 47,519Y Y `4 Claims. (cl. '1a-359) This invention relates to temperature indicatnot only relatively inaccurate as usually applied, l ing devices and more particularly is directed to but also require the load to be dropped from the indicators of this type -for measuring the temline before the thermometers can be installed in peratures on high voltage busses, switches, tertheir propel position.

5 minal connections of oil circuit breakers, bush- The present invention enables the operator to 5 ings of breakers and transformers, joints and read directlyvthe degree of temperature rise ,of high voltage current conducting circuits, and in the particular part of the apparatus being tested general for use in connection with electrical With respect t0 the SllrrOllildllg ambient tem- 'apparatus carrying high voltage current, perature during high voltage circuit conditions,

In the standardization of electrical equipment, even in circuits in which the voltage may be of 10 the electrical engineering industry has required the order of 25,000 volts. 'I'his reading affOIdS that the various circuit conductors and control an immediate indication of whether or not that equipment provided in power transmission and portion of the apparatus being tested is Within distribution systems and the like shall be of a the maximum allowable limits demanded for design such that at no time will the temperature apparatus of that design. Without the necessity 15 of any portion of the apparatus exceed 'more for further calculation. Such direct reading fathan a predetermined maximum with res'pect to cilitates the taking of a large number of readings the circumambient temperature. The present of diferent'portiohs of the apparatus in a re1- indicating device is adapted to facilitate quick` atvely ShOTt time. ItS 115e lll this manner, that and simple ascertainment of the temperatures of iS, t0 measure the degree 0f temperature rise 20 ahy eXp'OSed part of the apparatus, whereby a above the surrounding ambient temperature, is circuit or distribution system, and its associated obviously not limited only to the testing of high apparatus, can be readily checked to see that it Voltage electleal apparatus is in accordance with the requirements, and that The present invention. in its preferred embodithe particular control apparatus employed is ment, comprises a thermO-eouple mounted in 25 properly designed for the service expected of it. the vend of an insulated rod, with leads carried In recent times another Serious problem has Within the rod and leading t0 a. Sensitive milliarisen in connection with the power distribution voltmeter :which is mounted on the rod and so and Control systems operated by power cominsulated as to be capable of safe use with high panics. These companies have been making an voltages. The device includes a second insulat- 30 increasingly prevalent practice of overloading ing rod extending from the millivoltmeter housthe copper in circuits rather than replacing old ing t0 prbvlde a Safe and COIlVelient means OI equipment and buying and installing new orv adholding and placing the instrument in operating ditional equipment. Many busses and connecposition', and including a guarded handle portion tions in existing systems are now overloaded bewhich may be grasped by the operator. 35 yond their capacity, and hot spots and localized The end of the rod in which the thermo-couple faults occur much more frequently than in the is mounted preferably includes a resiliently suppast. This condition has been further aggraported tip with a spring of definite initial bias vated, in many instances, by a neglect of the necto facilitatethe setting-up of a minimum contact 40 essary maintenance inspection and repair serpressure between the thermo-couple and the obl 40 vice. In order to determine the predominating ject under observaton. This is desirable in order Weak spots in such systems, it has heretofore to fix the value of the' small temperature gradient been the practice to drop the load on the circuit, at the point of contact, thus contributing to install thermometers'in proper contacting posigreater accuracy in the temperature readings.

tion with dierent portions of the apparatus to IThe resiliently supported tip also allows the de- 45 be tested, and then reestablish the load and wait vice to be applied to an object without slipping until the thermometers have reacheda constant off the instant the pressure is relaxed to some temperature. extent.

With the present invention, facility in the Another feature of the present invention re- 56 testing and' determining of the temperature risc sides in the particular method of connecting the 50 of the various portions of the apparatus is p'rotwo insulating rods or tubes through the casing. vided, without the necessity of dropping the load, so as to secure adequate mechanical strength and a large number of such points may be measwithout relying entirely upon the millivoltmeter ured in a relatively short time. The device thus casing.

5. eliminates the use of thermometers, which are A still further advantage secured by the pres- M I ond vinsulating tube I1.

ent invention is the positioning of the instrument casing angularly with respect to the longitudinal axis of the indicating device, so that positioning of the' device is expedited, and ready sighting of the instrument reading with respect to the tip of the instrument is attained.

Other objects and advantages of the present invention will appear morefully from the following detailed description, which, taken in connection with the accompanying drawing, will disclose to those skilled in the art the particular construction and operation of a prefered form of the presentv invention.

In the drawing:

Figure 1 is a perspective view of the temperature indicator disposed in operating position for measuring the temperature of a contact clip;

Figure 2 is a sectional view through the tip end of the instrument;

Figure 3 is a partial sectional view through the millivoltmeter casing, and the associated connections of the insulating tube; andv Figure 4 is a diagrammatic View showing the circuit connections for the millivoltmeter.

Referring now to the drawing, in Figure 1 I have shown a switching apparatus comprising a base member 5 having a pair of insulators 6 mounted thereon, the insulators 6 having contact clip portions 1 adapted to have a switch blade 8 pivoted thereon for connection therebetween. Suitable leads 9 may extend from the contact clips for completing the circuit connections of the switch.

vThe indicating instrument comprises` a handlel portion III-provided with an annularly extending guard flange I2 positioned a shortdistance from the end of the handle portion I8, and an insulat-` ing tube I3 extending into an angularly offset socket portion I4 of the millivoltmeter housing I5. From the opposite end of the millivoltmeter housing I5 there extends a second angularly offset socket portion I 8, within which is secured a sec- The tube I1 extends'into proximity to the particular apparatus being tested, and is provided at its end with a projecting tip portion I8 adapted to have contact engagement with the particular portion of the apparatus being tested. In this embodiment of the invention the tip I8 engages one of the contact clips 1 for ascertaining the temperature of this clip during high voltage circuit conditions.

v'In Figure 2 I have disclosed the particular construction of the tip and insulating rod I1. It will be noted that the rod I1, which is formed of a .brous material or a molded phenol condensation product or the like, comprises an elongated hollow cylindrical tube which is preferably provided at material, and is provided with an inwardly pro` jecting flanged portion 23 extending inwardly of its end with a reduced annular portion' adapted to receive an end cap member 20. The cap member .is preferably secured to the tube I1 by means of the pin 22 extending thereacross.

The cap member 20 is also formed of insulating portion 23 of the cap member 20. 'I'he projecting stud portion is adapted to carry the thermocouple conductors 21 and 28, which are preferably joined at 29 to provide a thermo-couple outwardly of the projecting end of the carrier 25.

While thethermo-couple leads 21 and 28 may be formed of any dissimilar metals which are capable, when heated at their junction, of producing an electric current, I have found that satisfactory results are obtained by making the conductor 21, for example, of chromel, while the conductor or lead 28 may be of onstantan. The carrier member 25 is provided with a pair of recessed portions 30, into which the leads 21or 28 extend, the leads being preferably distorted in a suitable manner within the recesses so as to be keyed therein by means of insulating compound 32 which may be poured into therecesses 3U after the leads have been properly positioned therein. The leads 21 and 28 are provided with suitable insulation 33 and 34, to separate the free portions 4of said leads extending through the tubular insulating rod I1.

In order to provide for resilient movement of the tip 25 with respect to the end cap 20 of the tube I1, the tip is provided with an annularly reduced portion 35, which forms a shoulder 36 intermediate the ends of that portion of the member which is disposed within the interior of the tube I1. A suitable spring 31 is biased between the shoulder 36 and the pin member 22, and provides for movement of the member 25 inwardly of the tube I1 against the pressure of the spring member 31. 'Ihe tip 25 is normally forced into pressure engagement with the object with which perature gradient which has been found to vary substantially inversely with the contact pressure. Thus the temperature attained by the probing thermo-couple under any particular condition of test is. rendered more accurate and the consistency of the readings is greatly improved.

Another object of providing the resiliency in the tip construction is to prevent slippage of the tip, which would be likely to occur if a rigid assemblywere used and the operator relaxed the applied pressure by a slight movementfof his hand.

YIn Figure 3 I have disclosed the particular connection of the tubes I3 and I1 to the millivoltmeter casing I5, and the manner in which the millivoltmeter is mounted within its casing. The tube' I1 projects into the socket I6, and extends inwardly into the interior portion 38 of the millivoltmeter casing I5. Preferably, the inwardly extending end of the tube I1 is provided with an annular groove, which groove is adapted to be engaged by a suitable lockingpin or ball member 39 to lock the tube I1 Within the boss I6 and prevent outward displacement thereof. 'I'he conductors 21 and 28, extending from the thermo-couple 29, continue through the tube I1, and the conductor 28 is directly connected, as shown at 40, to one terminal of a millivoltmeter 42,-Which'mil1ivoltmeter is preferably of a highly sensitive type capable of registering accurately the electromotive force produced by heat` ing of the junction 29 of the instrument.

The conductor 21, which, as noted before, is preferably formed of chromel, is connected, as shown at 43, to a second conductor 44, which is formed on constantan and which is connected, as shown at 45, to the other terminal of the millivoltmeter 42. Any other equivalent thermocouple junction may be provided, and may be disposed in a suitable manner either in the tube I1 or the housing I5, as desired.'

In the operation of this circuit, the thermocouple 29 generates an electromotive force substantially directly proportional to the temperature of the particular object under test, in this case the contact clip 1. The thermo-couple 43 generates an electromotive force proportional to the temperature of the surrounding room or atmosphere, which may be termed the circumambient temperature, inasmuch as this thermocouple is located at a sufcient distance from the object being tested to prevent any appreciable heat transfer from the tip portion I8 of the device through the thermo-couple 43. The electromotive force generated by the thermo-,couple 43 is opposing the electromotive force generated by the thermo-couple 29. Thus the electromotive force at the meter terminals will be a function of the difference between these two forces, or proportional to the temperature rise, ,comprising the difference in temperature between the clip 1 and the surrounding room temperature. The

millivoltmeter 42 may be calibrated to provide for a direct reading of this temperature rise, which will be the increase in temperature of the contact clip, for example, with reference to--the surrounding temperature. Thus, if the standard requirements of contact clips of 'this type should be such that they should not have a temcircuit, the two junctions formed at the binding posts would be the equivalent of a junction directly between the two wires 21--and 28 but of opposite polarity and generating an electromotive force as a function ofthe temperature of the binding post; thus, the electromotive force imposed on the meter w`ou1d be substantially proportional to the temperature rise' of the probing junction. However, owing to the relatively large bulk of the binding posts and the adjoining parts of the meter, the junctions providing the temperature level of reference would be rather sluggish in adjusting themselves to a changing ambient temperature.

For this reason the thermo-couple 43 has been included to form a reference couple at some distance from the binding posts, thereby providing a couple of reference adhering more closely to a changing ambient temperature.

As shown in Figure 3, the millivoltmeter housing I5 preferably comprises a substantially cylindrical housing having an integrally formed rear wall 48, and provided with an exteriorlyl threaded portion 49 adjacent the forward end of the housing. A suitable glass cover plateV 50 is disposed in abutting engagement with the open end of the housing I5, and is secured in,

position by means of the flanged cap member 52, which has the inwardly extending beveled ange ber 54 interposed therebetween. Threading of the cap member 52 upon the threaded end 49 of the housing I5 clamps the glass 50 in position between-the end of the housing and the flanged portion 53 of the cap 52.

,The housing I5 is preferably formed of a molded phenol condensation product,A although it may be built up of any suitable or equivalent type of insulating material.

The millivoltmeter 42 is provided with a flanged cap member 55, having a projecting annular ange, which ange is provided, at spaced intervals about its periphery, with openings adapted to receive securing screws 56. An annular groove 51 formed in the inner surface of the cylindrical portion of thev housing I5 is adapted to receive a clamping ring 58, which projects outwardly of the groove 51 into the interior of the housing. A pair of supporting annular plate members 59, or the like, are disposed upon opposite sides of the ring 58, and are provided with enlarged central openings through` proper position within the housing I5. This disposes the face portion of the millivoltmeter 42, shown at 60 in Figure 4, in proper position so that it may be easily read through the glass 50. The particular spacing of the millivoltmeter with respect to the front of the housing is determined by the leakage distance required in an instrument of any particular voltage rating.

The casing I5 is also provided with an extending web portion 62, which terminates in the angularly offset socket portion I4, which socket portion is also provided with integral reinforcing webs 63 extending normal to the web 62. This provides proper reinforced support of the socket portion I4 of the housing I5 with respect to the body of the housing, and theentire housing I5,

with the projecting sockets I4 and I6, may thus o be molded integrally from a phenol condensation product or` similar insulating material.

The socket I4 is recessed to receive the extending end of the insulating tube I 3, and at its inner end has a recessed portion receiving an interiorly threaded nut member 64, which nut member is secured against rotation within the recessed portion of the socket I4, and is adapted to receive the projecting threaded stud 65 carried by the end of the tube I3. Thus the tube I3 is inserted into the socket I4, andthe threaded end 65 thereof is threaded into the retaining nut 6 4, preferably molded integrally with the socket I4, whereby the tube or rod I3 is fixedlysecured with respect to the housing I5, and extends in the oppoalinement with 'portion I0, there being the annular guard flange I2 interposed therebetween for preventing the operator from grasping the instrument close to the casing I5, whereby he might not be properly insulated from the high voltage currents passing through the apparatus being tested'.

By the angular disposition of the axis of the casing I5 with respect to the longitudinal axis of the tubes I3 and I1, facility in reading the in strument face 60 of the millivoltmeter 42 through the glass 50 is provided, since the operator may sight the point I8 of the instrument upon the portion of the apparatus being tested, and in his direct line of vision will appear the reading upon the instrument face 60 of the millivoltmeter through the glass 50, inasmuch as the glass is angularly offset with respect to the. longitudinalaxes of the members I3 and I'I. Further, this provides for reading of the instrument without interference from the guard ilange I2.

It is to be understood that the tube II need I not be a straight longitudinally extending tube,

but may be provided with a normally extending portion, whereby portions of apparatus accessible only by vertical insertion of the contacting thermocouple tip may beaccurately tested, merely by vertical movement of the normally extending portion of the tube I'I when such modified form of tube is provided. Further, if desired, the thermocouple junction I3 may be ventilated by means of suitable perforations in the casing I5 or the tube Il, or in any other equivalent Inanner, so as to insure that it remains at normal ambient temperature.

While I have shown and described only a preferred embodiment of the present invention, it is to be understood that various changes and modications may be made without departing from the underlying principles of the invention. For example, the millivoltmeter casing I5 may have its axis disposed in parallel Valinement with the axes of the tubes I3 and II, if desired for particular purposes, without departing from the scope of the present invention. I therefore do not intend to be limited to the particular structure disclosed, but only insofar as dened by the scope and spirit of the appended claims.

I claim:

1. Apparatus for measuring the temperature of electrically energized members comprising, in

combination, an insulating tube, a handle member, an instrument housing supported between adjacent ends of said tube and handle member, an instrument in said housing, a tip having telescoping engagement with the opposite end of said tube and resiliently supported therein, a thermocouple junction carried by said tip, and conductors leading from said junction to said instrument and carried within said tube. l

2. Apparatus for measuring the temperature of electrically energized members comprising, in combination, a pair of insulating tubes, an insulating housing, said tubes extending outwardly of said housing in opposite directions, a tip resiliently and slidably supported in the outer end of one of said tubes, a thermo-couple junction carried by said tip, an instrument in said housing, a second thermo-couple junction thermally remote from said rst junction and said housing, and' conductors connecting said thermocouple junctions to said instrument.

3. Apparatus for measuring the temperature of electrically energized members comprising, in combination, an insulating instrument housing having a socket, an insulating tube extending into said socket, a tip member slidably mounted in the outer end of said tube, spring means normally urging said tip outwardly of said tube, an instrument in said housing', a thermo-electric circuit leading from said instrument through said tube to said tip, and an exposed thermo-couple i junction at the outer end of the tip.

4. A hot-'junction mounting for a high ltension circuit temperature indicating device including an insulating tube having a radially inwardly ex- WASHINGTON W. PARKER. t 

